In signal transmission by means of multipole connectors in general and by means of connectors for data transmission in particular, for example, with connectors that meet the RJ45 standard, there is the problem that crosstalk of signals between the individual signal leads can occur because of capacitive and inductive coupling. Both types of coupling are based on the effect that an alternating voltage applied to a conductor leads to electric (capacitive coupling) or magnetic (inductive coupling) stray fields in the area of the conductor, which in particular in a spatially closely adjacent second conductor lead to the occurrence of an alternating voltage which can be misinterpreted as a signal on this conductor.
In general, capacitive and inductive coupling become stronger when the signal transmission occurs at higher frequencies. The inductive coupling is thereby particularly promoted by the parallel routing of conductor paths, while the capacitive coupling preferably occurs with the occurrence of areas of the conductor paths arranged parallel to one another.
Since with signal transmission and in particular inside connectors transmission signals and received signals are often transmitted in adjacent pairs of wires, with interference signals produced by crosstalk, an undesirable and—for a number of applications—unacceptable distortion in particular of the received signal occurs.
In order to characterize and to quantify this effect for a given connector, the value near-end cross-talk or near-end cross-talk attenuation (NEXT) is used. Near-end cross-talk is defined as the ratio of the level of the useful signal to the level of the interspersed signal of the interference, measured at the same end of the cable, given in decibels (dB). This variable, sometimes also called transverse attenuation, is a gauge of the suppression of the cross-talk between two adjacent pairs of wires. The stronger the cross talk is suppressed, the better the near-end cross-talk.
There are a number of known measures against the occurrence of crosstalk and thus for the improvement of near-end cross-talk. Probably the most elementary of these measures lies in the attempt to effectively prevent the coupling-in of interference signals. This approach is pursued, for example, with the use of twisted pair lines in which the wires of individual pairs of wires are twisted to one another and different pairs of wires with different lengths of twist are twisted with one another. This arrangement makes the coupling-in of interfering signals through inductive couplings much more difficult.
It is likewise known to provide a negative feedback in a targeted manner with which the level of the interference signal caused by crosstalk can be efficiently reduced. With this approach a capacitive or inductive coupling is deliberately produced. A capacitive coupling is realized thereby in that e.g., conductor paths between which the capacitive coupling is to be produced are provided with surfaces that are arranged parallel to one another in different layers. The inductive coupling between two conductor paths is produced in that the respective paths are guided at a small spatial distance running parallel to one another over a distance in a targeted manner.